In known electronic gear control systems, the up shift into the next higher gear occurs in dependence upon the engine speed, the load, and the vehicle speeds, as plotted along so-called upshift curves. To prevent engine damage, the curve generally specifies an engine speed which is less than the actual maximum permissible speed of the engine, to prevent tolerances in the electronic control from resulting in an excess engine speed and thereby damage to the engine.
A system is disclosed in DT-OS No. 2,023,877 in which the controlled or governed maximum controlled or governed speed at which the upshift occurs is increased when the vehicle accelerates. Thus, for fast acceleration, the speed range actually available in the engine is more fully utilized. The control described in this publication is particularly applicable to engines in which the fuel supply is decreased if the engine speed exceeds the maximum permissible engine speed. It is a disadvantage of this known method that it is only operative when the vehicle accelerates, but not when the pedal is put fully down to the floor board as, for example, may occur when driving up a mountain. Under the latter condition, the acceleration of the vehicle may be so small that the upshift does not occur even though the additional torque which would result from utilization of the full engine speed prior to upshifting is required and the pedal is at full load.
In known systems, if the speed at which the control operates to effect the upshift is too close to the speed at which the speed limiter sets in, it can happen that the fuel supply to the motor is decreased before the control system has had a chance to engage the next higher gear. In the known systems this can happen even though the pedal is at the full-load position or the kickdown switch has been activated. Thus, in spite of the full-load pedal position, in the known systems the gear control will never be able to reach the point at which the upshift occurs. For this reason, the upshift point for the gear control must be at a sufficiently low engine speed that the additive tolerances of the control and of the speed limiter will not prevent an upshift when the pedal is at the full-load position. In the known equipment, the full speed and torque range of the engine is therefore not utilized.